Graham Onions, Durham's veteran quick bowler, has become the latest senior player to announce his departure from Chester-le-Street, meaning that this week's final County Championship match of the season, against Worcestershire at New Road, will be his 139th and final appearance for a club he has represented with distinction since 2004.

Onions, who played nine Tests and four ODIs for England between 2009 and 2012, was unable to agree terms over the second year of a two-year deal and joins a mass exodus of players that already includes the top-order batsmen, Mark Stoneman and Scott Borthwick, who left for Surrey last season, and the T20 captain, Paul Coughlin, who is headed for Nottinghamshire. Keaton Jennings, the one-day captain and recent England opener, is also expected to move to Notts, albeit that depends on their promotion to Division One of the County Championship.

It is not yet confirmed where Onions, 35, is headed for the 2018 season, although both Lancashire and Kent are thought to be possible destinations for one of county cricket's most reliable performers.

The move is another body-blow for a club that has been left reeling since its enforced relegation from the top flight of the Championship last season, and subsequent points deduction, as punishment for requiring a financial bail-out from the ECB. Last week, Ian Botham, the club president, warned that the drain of so many senior players would have a devastating long-term effect on Durham's ability to uphold the standards of an academy that has produced several of the most talented England players of the past decade..

"We need senior players in the dressing room and, at the moment, I'm losing them left right and centre" said Botham. "I feel very sorry for the coaching staff and academy, because they aren't seeing their achievements come to fruition."

Onions, who was one of those academy graduates, has taken a club-record 522 first-class wickets for Durham in a career that has encompassed three County Championship titles between 2008 and 2013. His career-best figures of 9 for 67 came against Nottinghamshire in 2012, en route to a season's haul of 72 wickets. He went one better in 2013, when he was named the PCA's County Championship bowler of the season for his role in Durham's third title in six years.

Durham had been understandably keen to retain the services of their senior bowler, who was out of contract at the end of this season. Although they were able to agree financial terms for the 2018 season only, talks broke down over the offer of a two-year extension - the second year had been conditional on Onions avoiding serious injury in year one, having missed a month earlier this summer with a back problem.

A further stumbling block came with the long-term planning for Onions' post-playing career. While Durham had been keen to support him in pursuing a coaching career once he hangs up his boots, they were unable to give any guarantees about a place on the county coaching staff.

"At such an important point in his career DCCC understand Graham's desire to maximise his security," said the club in a statement. "Graham has played a huge part in the history of Durham County Cricket Club since making his first-class debut in 2004. He was part of the County Championship winning side in 2008, 2009 and 2013 and helped Durham win the Royal London One Day Cup in 2014.

"DCCC are extremely proud of Graham's development that saw him play Test cricket for England and recently become Durham's leading first-class wicket-taker. The club would like to thank Graham for his exceptional service and wish him well for the future."

Onions said: "It has been the hardest decision I have ever had to make. I genuinely love Durham County Cricket Club and hoped to finish my career here.

"Unfortunately, we were unable to agree on the length of contract and there doesn't appear to be any guaranteed opportunities for a coaching role in the future.

"So, with a heavy heart I have to leave Durham to ensure a securer future for my family. I would like to thank the club and the members for your support over the last 15 years.

"I hope I will be remembered for wearing the Durham badge with pride and always giving 100%. Durham will always hold a special place in my heart and I hope to return one day".